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Freestanding mixed tuned blade

  • US 5,286,168 A
  • Filed: 01/31/1992
  • Issued: 02/15/1994
  • Est. Priority Date: 01/31/1992
  • Status: Expired due to Term
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First Claim
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1. Rotating blades for a steam turbine comprising:

  • first and second blades, each having a platform portion with upper and lower surfaces;

    a straight side-entry root portion extending downwardly from the lower surface of the platform position; and

    a freestanding airfoil portion extending upwardly from the upper surface of the platform portion;

    wherein the airfoil portion has a leading edge, a trailing edge, a concave pressure side, a convex suction side, a base section and a tip section,wherein the base section of the second blade has an airfoil maximum thickness dimension that is less than an airfoil maximum thickness dimension of the base section of the first blade, and wherein the tip section of the first and second blades has a profile and the profile of the second blade is shorter in the longitudinal direction of the blade than a profile of the first blade,wherein the first and second blades have a resonant frequency in a first vibratory mode, corresponding to a tangential vibration in a rotational direction of a rotor on which the first and second blades are to be mounted when the rotor is operated at a running speed, which is substantially between a third and fourth harmonic of the running speed, and the first and second blades have a resonant frequency in a second vibratory mode, corresponding to a vibration in an axial direction of the rotor when the rotor is operated at the running speed, which is substantially midway between a seventh and eighth harmonic of the running speed.

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